IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Role of the photoreceptors from Pseudomonas syringae pv. tomato in bacterial physiology
Autor/es:
MOYANO L.; KRAISELBURD I; ARANA MR; GÄRTNER W; ORELLANO EG
Lugar:
Córdoba
Reunión:
Congreso; Segunda Reunión de Fotobiólogos Moleculares (GRAFOB); 2013
Resumen:
Light is an important environmental signal for almost all living organisms. Light perception is achieved by photoreceptor proteins that belong to one of six families depending on the structure of their chromophore: rhodopsins, phytocromes, xantopsins, cryptochomes, LOVs (Light, Oxygen and Voltage) and BLUFs (Bluf-Light sensing Using Flavin) proteins (1). Bacteriophytochromes (Bph) use a linear tetrapyrrole (bilin) as a chromophore bound via a thioether linkage. These photoreceptors are capable of photoconvert between red-absorbing (Pr) and far-red-absorbing (Pfr) states. In the Pr form the chromophore presents an extended all-cis configuration. Upon absorption of red light a cis-to-trans change in the configuration occurs, rendering the Pfr form. The Pfr form slowly reverts back in the dark (on a time scale of hours) or almost instantaneously upon absorption of far-red light (1). LOV-domain proteins are blue-light photoreceptors that were first described in plant phototropins and then found in many bacteria. LOV domains contain a molecule of flavin mononucleotide (FMN) as a non-covalently bound chromophore. The absorption of blue light triggers a photocycle that involves the formation of a covalent bound between a carbon atom of FMN and a conserved cystein residue of the protein. The covalent form represents the active state of the protein and slowly recovers to the dark state (2). Recent studies in pathogenic bacteria revealed the participation of bacterial photoreceptors, specifically from the LOV, BLUF and phytochrome families in bacterial virulence. This was demonstrated in pathogens, such as Xanthomonas citri subsp citri, Brucella abortus, Acinetobacter baumanni and, Agrobacterium tumefaciens (3-6). Pseudomonas syringae pv. tomato is an economically important plant pathogen. Its Genome contains several genes encoding putative photoreceptors. These include one gene encoding a blue light photoreceptor (LOV-domain protein) and two red/far red light photoreceptors (Bph1 and Bph2). The bacterium also carries a gene encoding a putative hemoxigenase protein (BphO) involved in the production of biliverdin, used as a chromophore by the bacterial phytochromes. The BphO gene is located next to the Bphy1 gene, probably belonging to the same operon unit. In this work we perform a physiological characterization of four mutants of P. syringae pv. tomato corresponding to knock out mutants of the LOV and Bhp photoreceptors and the BphO protein. The development of the disease in host plants by P. syringae pv. tomato requires a successful epiphytic survival (7). For this reason we evaluated bacterial features involved in this initial stage of the infection, leading to the establishment of the bacterium in the plant surface. These include bacterial motility, adhesion and biofilm formation which were modified in some of these mutants.